Catalyst for dehydrogenation of c6-c8 linear alkanes to aromatics and method for its preparation

Abstract

A catalyst for preparing aromatic hydrocarbon from C6-C8 linear alkane, comprising an active component and a carrier, wherein the active component comprises one or more than one combination of CrO x , VO x , MoO x or WO x , and the carrier is Al2O3, SiO2, ZrO2 or MgAl2O4, wherein the content of the active component oxide in the catalyst is 1-25wt%, and the rest is the carrier. The catalyst uses non-noble metal elements as the active component, thereby reducing the preparation cost. The catalyst improves the selectivity of aromatic hydrocarbon.

Description

TECHNICAL FIELD

[0001] The present application relates to a catalyst in the field of chemical industry, in particular, to a catalyst for preparing aromatic hydrocarbons by dehydrogenation of linear alkanes and a preparation method thereof. BACKGROUND

[0002] Aromatic hydrocarbons are important basic raw materials in modern chemical industry, which are widely used in the basic manufacturing of chemical industry. The production and scale of light aromatic hydrocarbons such as BTX (benzene, toluene and xylene) and ethylbenzene are only inferior to ethylene and propylene. The traditional production of BTX mainly comes from catalytic reforming process. Naphtha, catalytic gasoline and the like are converted into aromatic hydrocarbons and high-octane gasoline components on a bifunctional catalyst with noble metal Pt as a dehydrogenation component and halogen (Cl / F) to provide acidity. This patent technology is mainly mastered by UOP Company and IFP Company of France, such as US3915845, US6605566; EP0901814A1, CN96103410.6, CN02809057.8 and the like. However, the catalytic reforming process cannot effectively convert C6-C8 normal paraffins into aromatic hydrocarbons, and a large amount of raffinate oil is usually produced.

[0003] Low-carbon hydrocarbon aromatization is also one of the methods for producing BTX. The catalyst thereof is usually composed of a metal dehydrogenation center and a molecular sieve carrier capable of providing an acid center. Low-carbon alkanes are dehydrogenated to form low-carbon olefins at the dehydrogenation active center, and the olefins are then polymerized-cyclized to form aromatic hydrocarbons at the acid center. Chinese patent publication CN1232071A discloses a catalyst composed of Zn, rare earth, ZSM-5 molecular sieve and Al2O3, which is used for mixed C4 aromatization reaction at 500-550℃, and the aromatic hydrocarbon yield is greater than 40%, and the single-pass life of the catalyst is greater than 300h.

[0004] Chinese patent application publication CN112892585A discloses an ethane dehydrogenation aromatization catalyst of a modified high-silicon zeolite loaded with noble metal Pt, which has high BTX selectivity and low coke amount.

[0005] International application publication WO2005 / 065393 discloses a Pt / ZSM-5 catalyst for C1-C4 low-carbon hydrocarbon aromatization, which can significantly inhibit the generation of by-product methane.

[0006] Further, the researchers found that C6 and above straight-chain alkanes can be converted into aromatic hydrocarbons by dehydrogenation with high selectivity: n-hexane aromatization into benzene, n-heptane aromatization into toluene, n-octane aromatization into xylene and ethylbenzene, etc. Chinese patent application publication CN112473729A uses a Pt / KL catalyst for C6-C8 straight-chain alkane aromatization to produce BTX, in which the conversion rate of n-hexane is 3-4 times that of n-hexane in the reforming reaction, but the Pt loading in the catalyst is greater than 1%, and the catalyst cost is high. Chinese patent application publication CN111135858 uses a Pt / Kβ molecular sieve for long-chain alkane dehydrogenation aromatization, in which the toluene selectivity in n-heptane dehydrogenation aromatization can reach 85%, and the catalyst can be maintained for 170 h without deactivation, and the Pt loading in the catalyst is 1%-3%.

[0007] In the above catalysts for preparing aromatic hydrocarbons from C6 and above straight-chain alkanes, although the Pt / molecular sieve catalyst can convert straight-chain alkanes into aromatic hydrocarbons with high selectivity, it uses noble metal Pt as the active component, and the Pt content is not less than 1%, which results in high catalyst cost, and Pt is prone to sintering at high temperature, which leads to deactivation, and a large amount of hydrogen circulation is required in the reaction process to slow down the coking of the catalyst. A large amount of methane is produced in the carbon four aromatization process, and a large amount of hydrogen circulation is also required. Therefore, the catalyst for preparing aromatic hydrocarbons from C6 and above straight-chain alkanes needs to be further improved to avoid the use of noble metals or reduce the amount of noble metals. SUMMARY

[0008] An object of the present application is to provide a catalyst for preparing aromatic hydrocarbons from C6-C8 straight-chain alkanes, which uses a non-noble metal element as the active component to reduce the preparation cost.

[0009] Another object of the present application is to improve the selectivity of aromatic hydrocarbons by using the catalyst.

[0010] A catalyst for preparing aromatic hydrocarbons from C6-C8 straight-chain alkanes, comprising an active component and a carrier, wherein,

[0011] The active component comprises one or a combination of more than one of CrO x , VO x , MoO x or WO x , and the carrier is Al2O3, SiO2, ZrO2, or MgAl2O4.

[0012] In the catalyst, the content of the active component is 1-25 wt%.

[0013] Under the catalysis of the above catalyst, C6-C8 straight-chain alkanes are only prepared into aromatic hydrocarbons by dehydrogenation, and the selectivity of aromatic hydrocarbons with the same number of carbon atoms as the raw material is high. DETAILED DESCRIPTION

[0014] The catalyst for the preparation of aromatics from C6-C8 straight-chain alkanes according to this application is described in further detail below. This does not limit the scope of protection of this application, which is defined by the claims. Certain specific details disclosed provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments can be implemented using other materials, etc., without employing one or more of these specific details.

[0015] Unless the context otherwise requires, the terms “comprising” and “including” in the specification and claims shall be understood as open-ended and inclusive, meaning “including, but not limited to”.

[0016] The terms "implementation," "an implementation," "another implementation," or "certain implementations" used in this specification refer to specific features, structures, or characteristics described in relation to the implementation, which are included in at least one implementation. Therefore, "implementation," "an implementation," "another implementation," or "certain implementations" do not necessarily all refer to the same implementation. Furthermore, specific features, structures, or characteristics can be combined in any way within one or more implementations. Each feature disclosed in this specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0017] The metal oxides of the active components in the catalysts of this application are typically relatively stable oxides.

[0018] The active components CrOx, VOx, MoOx, or WOx all exist in stable oxidation states. For example, CrOx mainly exists on the surface as stable Cr. 3+ It exists, and there is still a small amount of Cr. 6+ (Cr 6+ With Cr 3+ There exists a balance); V in VOx stabilizes V 5+ Mo exists in MoOx to stabilize Mo. 6+ In Wox, W is stable. 6+ exist.

[0019] The Al2O3 described in this application is a compound of Al and O. Aluminum oxide includes crystalline phases such as γ, α, δ, θ, and η, or a mixture of several crystalline phases. SiO2 is a compound of Si and O, and is amorphous.

[0020] The reaction processes of straight-chain alkanes with different carbon atom numbers are completely different. For example, C4 liquefied gas low alkanes can generate aromatic hydrocarbons only through the processes of dehydrogenation, oligomerization, cyclization and aromatization. The aromatization process of C6-C8 straight-chain alkanes mainly involves dehydrogenation. The catalyst provided in the present application is used for the aromatization of C6-C8 straight-chain alkanes.

[0021] The C6-C8 straight-chain alkanes in the present application include straight-chain hexane, straight-chain heptane or straight-chain octane.

[0022] The catalyst for preparing aromatic hydrocarbons from C6-C8 straight-chain alkanes in the present application comprises an active component and a carrier, wherein the active component comprises one or more combinations of CrO x , VO x , MoO x or WO x , and the carrier is Al2O3, SiO2, ZrO2 or MgAl2O4. In the catalyst, the content of the active component oxide is 1%-25wt%, and the rest is the carrier.

[0023] The content of the active component is based on the mass of the active metal oxide.

[0024] The morphology of the carrier Al2O3, SiO2, ZrO2 or MgAl2O4 in the present application only serves to load the active component and other components, facilitates the molding of the catalyst, and has basically no effect on the catalytic performance.

[0025] In some embodiments, the content of the active component oxide is 5%-20wt%.

[0026] The above catalyst in the present application can be used to dehydrogenate and aromatize C6-C8 straight-chain alkanes to prepare aromatic hydrocarbons with the same number of carbon atoms as the raw materials, thereby improving the conversion rate of straight-chain alkanes.

[0027] In the process of aromatization of straight-chain alkanes, alkanes in the catalytic reforming process are first dehydrogenated to olefins on a metal-acid bifunctional catalyst, and the olefins continue to isomerize on the acid center to finally generate aromatic hydrocarbons. The conversion efficiency of straight-chain alkanes is low. The light hydrocarbon aromatization process also consists of metal centers with dehydrogenation activity and an acid carrier. Alkanes are first dehydrogenated to olefins, and small molecule olefins then undergo polymerization, cyclization and other reactions on the acid center to generate aromatic hydrocarbons. The present application directly converts straight-chain alkanes into aromatic hydrocarbons with high selectivity through the continuous dehydrogenation path (alkane-olefin-diene- triene-aromatic hydrocarbon). Compared with the catalytic reforming and C4 aromatization processes, the atom utilization rate of straight-chain alkanes is high, and the dry gas byproduct is less.

[0028] Preferably, the active component of the catalyst is CrO x , or CrO x and VOx MoO x or WO x combinations thereof.

[0029] In some embodiments, the catalyst further comprises an additive A, and the additive A comprises an alkali metal or / and an alkaline earth metal.

[0030] Preferably, the content of the additive A in the catalyst is 0.5%-5wt%.

[0031] The content of the additive A is calculated according to the metal element.

[0032] The additive A is one or more of Na, K, Rb, Sc, Mg, Ca, Sr or Ba.

[0033] The additive A is an alkali metal or an alkaline earth metal, which can shield unnecessary acid sites on the surface of the catalyst, inhibit side reactions such as cracking and isomerization, and further improve the selectivity of aromatic hydrocarbons generated by continuous dehydrogenation; but the alkali metal / alkaline earth metal shields the B acid center of the catalyst side reaction, which also poisons part of the L acid center, and the L acid center is the key to the activation of hydrocarbon C-H, and the reduction of the L acid center reduces the conversion efficiency of hydrocarbons.

[0034] In some embodiments, the catalyst further comprises an additive B, and the additive B comprises two or more of Co, Ni, Cu, Zn, Ag, Sn, Fe, La or Ge.

[0035] Preferably, the content of the additive B in the catalyst is 0.1%-10wt%.

[0036] In some embodiments, the content of the additive B in the catalyst is 2.0%-6.0wt%.

[0037] The content of the additive B is calculated according to the metal element.

[0038] The introduction of the additive B can adjust the existing form of the active component, including valence and dispersion state and other factors, and under the joint action of the additive B and the active component, further promote the conversion of alkanes. Taking Cr as an example, the Cr species on the surface of the catalyst which has catalytic dehydrogenation activity is Cr 3+ , while Cr 3+ is divided into reduced Cr 3+ and non-reduced Cr 3+ according to the source, and is divided into different types according to the difference in interaction with the carrier or other different types of Cr species on the surface, among which α-Cr2O3 is a Cr species without catalytic activity, and the introduction of the additive B improves the balance between Cr species through the interaction between Cr species and the carrier, and promotes the conversion of alkanes.

[0039] In some embodiments, the catalyst further comprises the additive A and the additive B described above.

[0040] The active component of the catalyst is co-impregnated with the promoter A and the promoter B, which effectively controls the existence and dispersion state of the active species on the carrier, strengthens the dehydrogenation activity and aromatic selectivity of the catalyst, and further improves the conversion rate of C6-C8 linear alkanes and the selectivity of aromatic hydrocarbons.

[0041] The linear alkane dehydrogenation aromatic catalyst of the present application can be prepared by impregnation method, coprecipitation method or sol-gel method. The impregnation method is preferred, and the stepwise impregnation method is more preferred. A certain amount of reducing agent is introduced into the impregnation solution when impregnating the active component.

[0042] In another aspect, a method for preparing a catalyst for preparing aromatic hydrocarbons from C6-C8 linear alkanes is provided. The active component precursor is dissolved in a reducing solvent, or the active component precursor and the promoter A precursor are dissolved in a reducing solvent, and the obtained solution is impregnated on a carrier. After drying and calcination, the catalyst for preparing aromatic hydrocarbons from C6-C8 linear alkanes is obtained.

[0043] In a preferred embodiment, the catalyst comprises the promoter A and the promoter B, and the method for preparing the catalyst is as follows.

[0044] In some embodiments, a method for preparing a catalyst for preparing aromatic hydrocarbons from C6-C8 linear alkanes is provided. The active component precursor and the promoter A precursor are dissolved in a reducing solvent, and the obtained solution is impregnated on a carrier. Then, drying is performed to obtain carrier A. The solution of the promoter B precursor is impregnated on the carrier A, and after drying and calcination, the catalyst for preparing aromatic hydrocarbons from C6-C8 linear alkanes is obtained.

[0045] First, the active component and the promoter A are co-impregnated on the carrier. The active component is uniformly distributed, and the promoter A plays a role in poisoning the acidic center. The co-impregnation of the active component and the promoter A has better catalytic effect. The promoter B promotes the conversion of alkanes through the interaction with the active component. Experimental results show that the stepwise impregnation of the promoter B has better effect.

[0046] The carrier impregnated with the active component and the promoter A is dried at a temperature of 220-450°C to obtain carrier A.

[0047] Drying the carrier impregnated with the active component and the promoter at the above-mentioned temperature can avoid the oxidation of the valence state of the active component to a higher valence state and increase the difficulty of reduction. The balance between the original active component (such as Cr) species can be maintained. After the first impregnation, drying is performed at a temperature close to the decomposition temperature of the active component precursor salt (in the range of 80-180°C), and high-temperature calcination is performed after impregnating the promoter B. Experimental tests show that the catalyst prepared by the impregnation sequence and parameters in the preparation method has better performance.

[0048] Preferably, the drying temperature is controlled at 0.5-20h.

[0049] The active component precursor includes soluble salts containing Cr, V, Mo or W elements. For example, one or more of (NH4)2Cr2O7, (NH4)2CrO4, K2CrO4, K2Cr2O7, Cr(NO3)3.9H2O, (NH4)2MoO4, (NH4)6W7O24 and NH4VO3.

[0050] The precursor of the assistant A is a soluble nitrate, carbonate or chloride of alkali or alkaline earth metal. Preferably, the precursor of the assistant A is a nitrate or chloride of alkali or alkaline earth metal.

[0051] The precursor of the assistant B is a nitrate, acetate or chloride containing Co, Ni, Cu, Zn, Ag, Sn, Fe, La or Ge metal.

[0052] The reducing solution includes an aqueous solution containing ethylene glycol, glycerol, oxalic acid or citric acid component.

[0053] The catalyst of the present application includes an active component which is a variable valence metal. The active component in the precursor salt has different valence states, for example, Cr species in (NH4)2Cr2O7, (NH4)2CrO4, K2CrO4, K2Cr2O7, Cr(NO3)3.9H2O are Cr 6+ and Cr 3+ respectively. The use of the alcohol or organic acid based reducing solvent ensures that the active component in the precursor species has the same valence state before the impregnation process, avoiding the influence of different precursor salts on the prepared catalyst. On the other hand, the selected reducing solvent is an alcohol or organic acid. During the impregnation process, the alcohol hydroxyl or carboxyl group competes with the active component for adsorption, which is beneficial to the dispersion of the active component.

[0054] In some embodiments, the mass concentration of the reducing solution is 0.5wt.% to 30wt.%, preferably 2wt.% to 8wt.%.

[0055] In some embodiments, the carrier impregnated with the active component or impregnated with the active component and the assistant A, the assistant B is dried and calcined at a temperature of 550 to 750°C to obtain a catalyst for preparing aromatic hydrocarbons from C6-C8 linear alkanes.

[0056] The drying temperature is controlled in the range of 80 to 180°C.

[0057] Preferably, the calcination temperature is controlled for 2 to 10h.

[0058] In the process of preparing a catalyst for preparing aromatic hydrocarbons from C6-C8 linear alkanes, the amount of the active component precursor, the assistant A precursor and the assistant B precursor is selected according to the content of each component in the final catalyst required.

[0059] For example, the content of the active component oxide is 1% to 25% by weight; the content of the auxiliary A is 0.5% to 5% by weight; and the content of the auxiliary B is 0.1% to 10% by weight. The corresponding amount of the active component precursor, the auxiliary A precursor or the auxiliary B precursor is calculated.

[0060] In still another aspect, the catalyst is used in the reaction of C6-C8 straight chain alkanes to prepare aromatic hydrocarbons, and the reaction temperature is controlled at 450 to 600°C.

[0061] A method for preparing aromatic hydrocarbons from C6-C8 straight chain alkanes, which comprises preparing aromatic hydrocarbons from C6-C8 straight chain alkanes in the presence of the catalyst according to any one of claims 1 to 3, and controlling the reaction temperature at 450 to 600°C.

[0062] The reactor for the reaction of C6-C8 straight chain alkanes to prepare aromatic hydrocarbons by dehydrogenation can be a fixed bed reactor or a fluidized bed reactor.

[0063] In some embodiments, water vapor is fed simultaneously with the straight chain alkanes in the reaction of C6-C8 straight chain alkanes to prepare aromatic hydrocarbons by dehydrogenation. The ratio of alkanes / H2O (hydrocarbon / water ratio) is 10 to 1:1, preferably the ratio of hydrocarbon / H2O (hydrocarbon / water ratio) is 8 to 4:1.

[0064] The ratio of alkanes / H2O herein is a volume ratio.

[0065] With the addition of water vapor, the amount of carbon deposition as a byproduct is reduced, and the selectivity of the target product is correspondingly improved.

[0066] In the reaction of C6-C8 straight chain alkanes to prepare aromatic hydrocarbons according to the present application, water vapor is fed together with the hydrocarbons, the partial pressure of the alkanes is reduced, the carbon deposition and coking of the catalyst are slowed down, the amount of carbon deposition on the catalyst is small, the required coking temperature is low, and there is no need for hydrogen circulation or chlorination and acidification treatment.

[0067] In the reaction of C6-C8 straight chain alkanes to prepare aromatic hydrocarbons, the pressure is 0.05 to 0.3 MPa.

[0068] In the reaction of C6-C8 straight chain alkanes to prepare aromatic hydrocarbons, the mass space velocity is 0.1 to 10 h -1 .

[0069] The catalyst according to the present application is used in the continuous dehydrogenation of C6-C8 straight chain alkanes to prepare aromatic hydrocarbons, and is particularly suitable for the continuous dehydrogenation of n-hexane (C6) to prepare benzene. The conversion rate of n-hexane and the selectivity of benzene in the product can both be greater than 90%.

[0070] Compared with the catalysts in the prior art, the catalyst according to the present application has the following advantages:

[0071] The catalyst of the present application converts alkane into aromatic hydrocarbon with high selectivity by continuous dehydrogenation, and has high utilization rate of linear alkane atoms and less dry gas by-product.

[0072] In particular, by the combination of the active component and the auxiliary agent, the introduction of a reducing agent in the preparation process effectively controls the existence and dispersion state of the active species on the carrier, strengthens the dehydrogenation activity and aromatic hydrocarbon selectivity of the catalyst, and has excellent linear alkane dehydrogenation aromatization activity and aromatic hydrocarbon selectivity. In the reaction of dehydrogenation of n-hexane into benzene, the single-pass yield of benzene can reach 90%.

[0073] On the other hand, the active component of the catalyst is inexpensive, and is used for continuous dehydrogenation of linear alkane to produce aromatic hydrocarbon, and the catalyst cost is low compared with the catalytic reforming process.

[0074] The reaction process of the catalyst of the present application for dehydrogenation of linear alkane to produce aromatic hydrocarbon is operated at normal pressure, the raw material and water vapor are simultaneously introduced into the reactor, the catalyst has less carbon deposition, the required decoking temperature is low, and hydrogen circulation is not required, and chlorination and acidification treatment is not required. Compared with the catalytic reforming process and the C4 aromatization process, the linear alkane to aromatic hydrocarbon process has a simple process flow, no corrosion to the equipment, and low equipment investment.

[0075] In the catalyst prepared in the following examples, the content of the active component is the content of the stable oxide, and the content of the auxiliary agent A or the auxiliary agent B is the content of the element.

[0076] Example 1

[0077] 13g Cr(NO3)·9H2O and 2.75g Mg(NO3)2 were dissolved in 55ml 2.5% glycerol aqueous solution, and were impregnated into 100g Al2O3 powder in an equal volume, and were dried at 240℃ for 1h. 8.2g Ni(NO3)2·6H2O and 3.3g La(NO3)3·6H2O were dissolved in 80ml deionized water, and were impregnated into the above treated powder in an equal volume, and were dried at 80℃ for 6h, and were calcined at 550℃ for 4h, and were sieved to obtain a catalyst, which was recorded as catalyst A. In catalyst A, the content of chromium oxide was 6.7%, the content of Mg was 0.5%, the content of Ni was 1.7%, the content of La was 1.1%, and the rest was the carrier Al2O3.

[0078] Example 1-1

[0079] 13g Cr(NO3)·9H2O and 2.75g Mg(NO3)2 were dissolved in 55ml 2.5% glycerol aqueous solution, and were impregnated into 100g Al2O3 powder in an equal volume, and were dried at 240℃ for 1h, and were calcined at 550℃ for 4h, and were sieved to obtain a catalyst, which was recorded as catalyst B. In catalyst B, the content of chromium oxide was 6.7%, the content of Mg was 0.5%, and the rest was the carrier Al2O3.

[0080] Example 1-2

[0081] 13 g of Cr(NO3)3-9H2O was dissolved in 55 ml of 2.5% glycerol aqueous solution, and the same volume was impregnated into 100 g of Al2O3 powder, and dried at 240°C for 1 h. 8.2 g of Ni(NO3)2-6H2O and 3.3 g of La(NO3)3-6H2O were dissolved in 80 ml of deionized water, and the same volume was impregnated into the above treated powder, dried at 80°C for 6 h, calcined at 550°C for 4 h, and sieved by a molding screen to obtain a catalyst, which was designated as catalyst C. In catalyst C, the content of chromium oxide was 6.7%, the content of Ni was 1.7%, the content of La was 1.1%, and the rest was the carrier Al2O3.

[0082] Example 1-3

[0083] 13 g of Cr(NO3)3-9H2O was dissolved in 55 ml of 2.5% glycerol aqueous solution, and the same volume was impregnated into 100 g of Al2O3 powder, and dried at 80°C for 6 h, and calcined at 550°C for 4 h, and sieved by a molding screen to obtain a catalyst, which was designated as catalyst D. In catalyst D, the content of chromium oxide was 6.7%, and the rest was the carrier Al2O3.

[0084] The catalysts prepared in Example 1, Example 1-1, Example 1-2, and Example 1-3 were subjected to n-hexane aromatization.

[0085] The reaction process conditions were a reaction temperature of 600°C, a pressure of 0.2 MPa, a n-hexane mass hourly space velocity of 0.5 h-1, a hydrocarbon / H2O ratio in the feed of 3:1, and a reaction time of 0.2 h. The reaction results are shown in Table 1. -1

[0086] Example 2

[0087] 58.9 g of (NH4)2CrO4 and 3.7 g of KCl were dissolved in 80 ml of 5% ethylene glycol aqueous solution, and the same volume was impregnated into 100 g of Al2O3-ZrO2 powder, and dried at 220°C for 4 h. 0.12 g of Cu(NO3)2-3H2O and 0.35 g of Co(NO3)2-6H2O were dissolved in 80 ml of deionized water, and the same volume was impregnated into the above treated powder, dried at 80°C for 4 h, calcined at 620°C for 6 h, and sieved by a molding screen to obtain a catalyst, which was designated as catalyst E. In catalyst E, the content of chromium oxide was 20.1%, the content of K was 1.9%, the content of Cu was 0.03%, the content of Co was 0.07%, and the rest was the carrier Al2O3-ZrO2.

[0088] Example 2-1 ​

[0089] 58.9 g of (NH4)2CrO4 and 3.7 g of KCl were dissolved in 80 ml of deionized water and impregnated into 100 g of Al2O3-ZrO2 powder by equal volume. The mixture was then dried at 300 °C for 4 h. 0.12 g of Cu(NO3)2·3H2O and 0.35 g of Co(NO3)2·6H2O were dissolved in 80 ml of deionized water and impregnated into the above-treated powder by equal volume. The powder was dried at 80 °C for 4 h, calcined at 620 °C for 6 h, and then sieved to obtain a catalyst, denoted as catalyst F. Catalyst F contains 20.1% chromium oxide, 1.9% K, 0.03% Cu, and 0.07% Co, with the remainder being the support Al2O3-ZrO2.

[0090] The catalysts prepared in Example 2 and Example 2-1 were subjected to n-heptane aromatization:

[0091] The reaction conditions were as follows: reaction temperature 500℃, pressure 0.11 MPa, and heptane mass hourly space velocity (HHSV) 1.0 h⁻¹. -1 The ratio of hydrocarbons to H₂O in the feed was 6:1, and the reaction time was 0.7 h. The reaction results are shown in Table 1.

[0092] Example 3

[0093] 17.7g CrO3 and 24.8g (NH4)6W7O 24 0.33 g of Sr(NO3)2 was dissolved in 80 ml of 8% citric acid aqueous solution and impregnated into 100 g of MgAl2O4 powder by equal volume. The powder was then dried at 450 °C for 6 h. 6.9 g of RbCl and 11.2 g of Fe(NO3)3·9H2O were dissolved in 70 ml of deionized water and impregnated into the above-treated powder by equal volume. The powder was dried at 120 °C for 3 h, calcined at 700 °C for 6 h, and the resulting product was shaped and sieved to obtain catalyst G. Catalyst G contains 13.4% chromium oxide, 2.5% tungsten oxide, 0.14% Sr, 4.9% Rb, and 1.55% Fe, with the remainder being a support.

[0094] Example 3-1

[0095] 70.8 g Cr(NO3)3.9H2O, 6.9 g RbCl, 11.2 g Fe(NO3)3.9H2O and 0.33 g Sr(NO3)2 were dissolved in 35 ml deionized water, and impregnated into 100 g MgAl2O4 powder with equal volume, dried at 120 °C for 3 h, calcined at 700 °C for 6 h, and sieved to get catalyst, which was marked as catalyst I. In catalyst I, the content of chromium oxide was 13.4%, the content of Sr was 0.14%, the content of Rb was 4.9%, the content of Fe was 1.55%, and the rest was carrier.

[0096] Example 3-2

[0097] 70.8 g Cr(NO3)3.9H2O, 6.9 g RbCl, 11.2 g Fe(NO3)3.9H2O and 0.33 g Sr(NO3)2 were dissolved in 35 ml 8% citric acid aqueous solution, and impregnated into 100 g MgAl2O4 powder with equal volume, dried at 120 °C for 3 h, calcined at 700 °C for 6 h, and sieved to get catalyst, which was marked as catalyst H. In catalyst H, the content of chromium oxide was 13.4%, the content of Sr was 0.14%, the content of Rb was 4.9%, the content of Fe was 1.55%, and the rest was carrier.

[0098] The catalysts prepared in example 3, example 3-1 and example 3-2 were subjected to n-octane aromatization:

[0099] The reaction process conditions were as follows: the reaction temperature was 565 °C, the pressure was 0.11 MPa, the mass space velocity of propane was 5.5 h-1, the hydrocarbon / H2O in the feed was 1:1, and the reaction time was 0.5 h. The reaction results are shown in Table 1. -1

[0100] Example 4

[0101] 23 g NH4VO3, 4.9 g Cr(NO3)3.9H2O and 3.3 g Na2CO3 were dissolved in 50 ml 1.5% oxalic acid aqueous solution, and impregnated into 100 g Al2O3-SiO2 powder with equal volume, dried at 240 °C for 4 h. 3.2 g La(NO3)3.6H2O and 41 g Zn(NO3)2.6H2O were dissolved in 70 ml deionized water, and impregnated into the above treated powder with equal volume, dried at 70 °C for 5 h, calcined at 650 °C for 6 h, and sieved to get catalyst, which was marked as catalyst J. In catalyst J, the content of chromium oxide was 0.95%, the content of vanadium oxide was 10%, the content of Na was 1.4%, the content of La was 1.0%, the content of Zn was 9.0%, and the rest was carrier.

[0102] Example 4-1 ​

[0103] 23 g NH4VO3, 4.9 g Cr(N03)3.9H2O and 3.3 g Na2CO3 were dissolved in 50 ml of aqueous solution, and the same volume was impregnated into 100 g of Al2O3-SiO2 powder, which was placed in an oven at 85°C for 4 h. 3.2 g La(N03)3.6H2O and 41 g Zn(N03)2.6H2O were dissolved in 70 ml of deionized water, and the same volume was impregnated into the above treated powder, which was dried at 70°C for 5 h and calcined at 650°C for 6 h. The catalyst was obtained by sieving and was recorded as catalyst K. In catalyst K, the content of chromium oxide was 0.95%, the content of vanadium oxide was 10%, the content of Na was 1.4%, the content of La was 1.0%, the content of Zn was 9.0%, and the rest was the carrier.

[0104] The catalyst prepared in Example 4 and Example 4-1 was subjected to n-hexane aromatization:

[0105] The reaction process conditions were that the reaction temperature was 520°C, the pressure was 0.10 MPa, the mass space velocity of n-hexane was 2.0 h-1, the hydrocarbon / H2O in the feed was 2:1, and the reaction time was 0.5 h. The reaction results are shown in Table 1. -1

[0106] Example 5

[0107] 37.7 g (NH4)2Cr2O4, 1.7 g (NH4)2MoO4, 2.82 g oxalic acid and 2.8 g CsNO3 were dissolved in 80 ml of deionized water, and the same volume was impregnated into 100 g of SiO2 powder, which was placed in an oven at 300°C for 1 h. 6.5 g Cu(N03)2.3H2O and 4.1 g C2H2O4Sn were dissolved in 80 ml of deionized water, and the same volume was impregnated into the above treated powder, which was dried at 60°C for 6 h and calcined at 650°C for 4 h. The catalyst was obtained by sieving and was recorded as catalyst L. In catalyst L, the content of chromium oxide was 18.9%, the content of molybdenum oxide was 0.83%, the content of Cs was 1.9%, the content of Cu was 1.7%, the content of Sn was 2.4%, and the rest was the carrier.

[0108] The catalyst prepared in Example 5 was subjected to n-hexane aromatization:

[0109] The reaction process conditions were that the reaction temperature was 500°C, the pressure was 0.10 MPa, the mass space velocity of n-hexane was 2.0 h-1, the hydrocarbon / H2O in the feed was 4:1, and the reaction time was 0.5 h. The reaction results are shown in Table 1. -1

[0110] Example 5-1

[0111] ​​37.7 g of (NH4)2Cr2O4, 1.7 g of (NH4)2MoO4, 2.82 g of oxalic acid and 2.8 g of CsNO3 were dissolved in 80 ml of deionized water, and the same volume was impregnated into 100 g of SiO2 powder, and placed in a 300°C oven for 1 h. 6.5 g of Cu(NO3)2-3H2O and 4.1 g of C2H2O4Sn were dissolved in 80 ml of deionized water, and the same volume was impregnated into the above treated powder, dried at 60°C for 6 h, calcined at 650°C for 4 h, and sieved by a molding screen to obtain a catalyst, which was designated as catalyst M. In catalyst M, the content of chromium oxide was 18.9%, the content of molybdenum oxide was 0.83%, the content of Cs was 1.9%, the content of Cu was 1.7%, the content of Sn was 2.4%, and the rest was the carrier.

[0112] The catalyst prepared in Example 5-1 was subjected to n-hexane aromatization:

[0113] The reaction process conditions were as follows: the reaction temperature was 500°C, the pressure was 0.10 MPa, and the n-hexane mass space velocity was 2.0 h -1 The reaction time was 0.5 h with no water vapor feed. The reaction results are shown in Table 1.

[0114] Example 6

[0115] 16.8 g of (NH4)2Cr2O7, 4.07 g of oxalic acid and 0.8 g of Ba(NO3)2, 1.4 g of CaCl2 were dissolved in 80 ml of deionized water, and the same volume was impregnated into 100 g of MgAl2O4-ZrO2 powder, and placed in a 350°C oven for 1 h. 4.4 g of AgNO3 and 3.5 g of C2H2O4Ge were dissolved in 80 ml of deionized water, and the same volume was impregnated into the above treated powder, dried at 60°C for 6 h, calcined at 650°C for 4 h, and sieved by a molding screen to obtain a catalyst, which was designated as catalyst N. In catalyst N, the content of chromium oxide was 5%, the content of Ba was 0.4%, the content of Ca was 0.5%, the content of Ag was 2.8%, the content of Ge was 2.0%, and the rest was the carrier.

[0116] Example 6-1

[0117] 16.8 g (NH4)2Cr207, 4.07 g oxalic acid and 0.8 g Ba(NO3)2, 1.4 g CaCl2 were dissolved in 80 ml deionized water, and the same volume was impregnated into 100 g ZrO2 powder, and then placed into a 350 °C oven for 1 h. 4.4 g AgNO3 and 3.5 g C2H2O4Ge were dissolved in 80 ml deionized water, and the same volume was impregnated into the above treated powder, dried at 60 °C for 6 h, calcined at 650 °C for 4 h, and then sieved to obtain a catalyst, which was recorded as catalyst O. The content of chromium oxide was 5%, the content of Ba was 0.4%, the content of Ca was 0.5%, the content of Ag was 2.8%, the content of Ge was 2.0%, and the rest was the carrier.

[0118] The catalyst prepared in Example 6, 6-1 was subjected to n-octane aromatization:

[0119] The reaction process conditions were as follows: the reaction temperature was 500 °C, the pressure was 0.10 MPa, the mass space velocity of n-octane was 2.0 h-1, the feed hydrocarbon / H2O was 10:1, and the reaction time was 0.5 h. The reaction results are shown in Table 1. -1

[0120] Table 1

[0121]

[0122] This example is implemented on the premise of the technical scheme of the present application, and gives a detailed implementation mode and process, but the protection scope of the present application is not limited to the above-mentioned examples.​

Claims

1. A process for the preparation of aromatic hydrocarbons from C6-C8 linear alkanes, characterized in that, C6-C8 linear alkanes are prepared into aromatic hydrocarbons by feeding C6-C8 linear alkanes and water vapor with a volume ratio of 10-1:1, under the action of a catalyst, and at a reaction temperature of 450-600℃; The catalyst comprises an active component, an auxiliary A, an auxiliary B and a carrier, wherein the active component comprises CrO x in combination with VO x , MoO x or WO x , the carrier is Al2O3, SiO2, ZrO2 or MgAl2O4; In the catalyst, the content of the active component oxide is 1%-25wt%; The assistant A includes an alkali metal or / and an alkaline earth metal, and the content of the assistant A is 0.5%-5wt%; The assistant B includes two or more than two of Co, Ni, Cu, Zn, Ag, Sn, Fe, La or Ge, and the content of the assistant B is 0.1%-10wt%; The rest is the carrier.

2. The method of claim 1, wherein, In the catalyst, the content of the active component oxide is 5%-20wt%.

3. The method of claim 1, wherein, The preparation method of the catalyst includes: The active component precursor and the assistant A precursor are dissolved in a reducing solution, the obtained solution is impregnated on the carrier, and then drying is performed to obtain carrier A; the solution of the assistant B precursor is impregnated on the carrier A, and drying and calcination are performed to obtain the catalyst for preparing C6-C8 linear alkanes into aromatic hydrocarbons; The active component precursor includes a soluble salt containing Cr, V, Mo or W elements; The precursor of the assistant A is a soluble nitrate, carbonate or hydrochloride of an alkali metal or an alkaline earth metal; The precursor of the assistant B is a nitrate, acetate or chloride containing Co, Ni, Cu, Zn, Ag, Sn, Fe, La or Ge metal.

4. The method of claim 3, wherein, The carrier impregnated with the active component and the assistant A is dried at a temperature of 220-450℃ for 0.5-20h to obtain carrier A.

5. The method of claim 3, wherein, The reducing solution includes an aqueous solution containing ethylene glycol, glycerol, oxalic acid or citric acid components.

6. The method of claim 5, wherein, The mass concentration of the reducing solution is 0.5wt.%-30wt.%.

7. The method of claim 5, wherein, The mass concentration of the reducing solution is 2wt.%-8wt.%.

8. The method according to any one of claims 3-6, characterized in that, After the solution of the assistant B precursor is impregnated on the carrier A, drying at 80-180℃ and calcination at a temperature of 550-750℃ are performed to obtain the catalyst for preparing C6-C8 linear alkanes into aromatic hydrocarbons.

9. The method of claim 1, wherein, In the reaction of preparing C6-C8 linear alkanes into aromatic hydrocarbons, the pressure is 0.05-0.3MPa.

10. The method of claim 1, wherein, The volume ratio of C6-C8 linear alkanes to water vapor is 8-4:1.

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